How can I implement an abstract singleton class in Java?

Question

Here is my sample abstract singleton class:

public abstract class A {
    protected static A instance;
    public static A getInstance() {
        return ins         


        

Answer 1

Abstract Singleton? Doesn't sound viable to me. The Singleton pattern requires a private constructor and this already makes subclassing impossible. You'll need to rethink your design. The Abstract Factory pattern may be more suitable for the particular purpose.